1. Field of the Invention
The invention relates to strains of the aerobic mycoparasitic fungus Coniothyrium minitans having .beta.-glucanase activity.
2. Description of the Related Art
A major factor affecting animal production is a efficiency of feed utilization. Efficient feed utilization requires efficient digestion of complex .beta.-glucan substrates that are present in forage. .beta.-glucans are one of the most abundant groups of naturally-occurring polysaccharides. .beta.-glucans with (1,3), (1,4), (1,6) and (1,2) linkages have been identified in both bacteria and plants (Stone and Clark 1992), while (1,3) and (1,6) linkages are abundant in fungal cell walls (Wessels and Sietsma 1981). Fibre and .beta.-glucans in feed are often poorly digested by animals, especially monogastric animals, resulting in waste. Diets containing certain forms of glucan (such as arabinoxylan in wheat and rye, or .beta.-glucan in barley and oats) may also have deleterious effects on nutrient absorption and may promote intestinal disturbances by enteric pathogens.
The digestion of fibre and .beta.-glucans in feed by livestock may be improved by enzyme supplementation (Shuttle 1995). Glycanolytic enzyme feed additives are thought to enhance fibre degradation and/or reduce viscosity in the gastrointestinal tract, thereby increasing feed intake and passage rate (Sears 1993). Currently, feed enzyme supplementation has been limited by the high cost of enzyme production. Industry relies on mass fermentation to produce feed enzymes and is limited to a small group of fungal (mainly Aspergillus, Penicillium and Trichoderma) and bacterial (Bacillus coagulans, B. lichenformis, B. circulansand B. subtilis var.) taxa as a source for these enzymes (Sears 1993). There is, therefore, an ongoing need for new microbial sources of .beta.-glucan degrading enzymes (.beta.-glucanases). Ideally, such microorganisms could be easily and inexpensively grown by liquid or solid state fermentation, and would have high levels of .beta.-glucanase activity. Endo- and exo-1,3-.beta.-glucanase activity have been reported in the aerobic mycoparasitic fungus Coniothyrium minitans (Jones et al. 1973). However, the Jones et al. reference does not teach combined endo-1,3- and endo-1,4- .beta.-glucanase activity of C. minitans. Combined endo-1,3- and endo-1,4-.beta.-glucanase activity is the .beta.-glucanase activity that is most useful for degrading .beta.-glucans in animal feeds. Further, as the medium on which the C. minitans cultures of Jones et al. were grown consisted substantially of sclerotia of Sclerotinia sclerotiorum, a natural .beta.-glucan source, the Jones et al. reference does not teach constitutive .beta.-glucanase activity of C. minitans on a rich medium without a .beta.-glucan source. Such a medium would be preferred for industrial fermentation applications. Teaching neither combined endo-1,3- and endo-1,4-.beta.-glucanase activity nor constitutive .beta.-glucanase activity of C. minitans, the Jones et al. reference does not suggest the utility of C. minitans as a useful source of .beta.-glucanase enzymes.